You can use a fence or plant a thorny hedge like barberry or lay stickery chicken wire or thorny rose branches on top of newly seeded soil, try red pepper flakes where they like to dig or spray them with water when they enter the garden. There are also some animal repellents that work on some dogs and cats. It will take about 3 weeks to retrain animals to find a new place to use as their powder room. Perhaps you can suggest to the owners to keep the pets at home. I use a combination of all of these but still some pets will visit and make deposits. Just glad they are not elephants. Keep growing, Marianne Binetti